Key-driven calculating machine



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KEY-DRIVEN CALCULATING MACHINE Filed Sept. 12, 1946 9 Sheets-Sheet 9 J22 ueizfor Jose W213 .VTarck Patented Apr. 3, 1951 KEY-DRIVEN CALCULATING MACHINE Joseph A. V. Turck, Wilmette, Ill., assignor to Felt & Tarrant Manufacturing Company, Chicago, 111., a corporation of Illinois Application September 12, 1946, Serial No. 696,517

42 Claims. 1

The invention relates to improvements in calculating machines and, more particularly, to the improvements in the key-driven type where additive actuation is created by the down key depression in setting up power in springs to give additive degrees of action on the up or return stroke of the actuating mechanism.

The principal object of the present invention is the provision of dual leverage action for each denominational order which may be set to give varying degrees of movement under action from the same key and to all the keys of each denominational order, according to whether they are to be used for negative or positive calculation. The purpose of the dual leverage is to provide an actuating mechanism for a key-driven calculator operated by a uni-marked keyboard, that is, a keyboard in which all keys, except the 9 keys, bear a single number, to save the operator the trouble of learning the use of the dual marking. Familiarity with, in efiect, two keyboards has been necessary in all key-driven calculating machines prior to the invention herein disclosed because of the dual complementary markings of each key. The touch system has always been complicated by the necessity of learning the touch of the dual marked keys on key-driven calculators and thus it is difficult to become adept in negative forms of calculation on account of the lack of continuity in formation of the key tops which serve in the positive forms of calculation only. The formation of the key tops with the use of the uni-marked keyboard of this invention provides a great advantage.

Another object of the invention is to provide mechanism by the means of which automatic subtraction may be accomplished on a keydriven calculator.

A third object of the invention is that of combining the scheme of the dual stop mechanism disclosed in the machine of my pending application Serial No. 494.907 of July 16, 1943, issued as Patent No. 2,527,467 on October 24, 1950, and a dual key-operated leverage action, and utilizing the means employed in the said application for bringing the stop actions into use, for jointly bringing into play the proper fulcrum to coact with each stop bar for positive forms of calculation, such as addition and multiplication, or for jointly bringing into play the fulcrum and the relative stop bar for negative forms of calculation, such as subtraction and division.

A. fourth object of invention is present in the means employed when a subtraction is made to delay the adding action until power is stored in such remaining orders of the machine as have not already had power stored in them by key depression in setting up the subtrahend, whereupon the said power in all orders is released automatically at the completion of the universal storing action.

A fifth object of the invention is that of the provision of means to prevent interference by the operator in supplying the auxiliary universal power to all the orders from holding any of the orders against free return by their normal means.

A sixth object of the invention is to provide an arrangement whereby the means for selecting the proper stop bar and fulcrum, the means for delaying the adding action in a subtractive operation, and the means for preventing interference by the operator with the free return of the mechanisms of each of the orders, are brought under control of an indicative manual setting device. The manual setting device also serves to clear and reset locks normally holding the manual means for supplying the auxiliary power against use except when the machine is pre-set for subtracting.

Another object is to provide a key-driven calculating machine embodying means for selectively controlling the degree of actuation of the accumulator mechanism by the keys whereby the same value markings serve to identify the keys for either additive or subtractive operations, thus eliminating the dual key markings heretofore required and enabling the operator to perform either type of calculation by the simple touch system used for adding.

Another object is to provide means settable so that the complemental rather than the numerical values of depressed keys are transferred to the accumulator mechanism immediately upon release of the keys to facilitate the performance of division.

Other objects and advantages of the invention will become apparent from the following detailed description of the preferred embodiment illustrated in the accompanying drawings, in which:

Figure 1 is a plan view of a key-driven calculating machine embodying the features of the invention. 7

Fig. 2 is an elevational view of the machine as viewed from the right side.

Fig. 3 is a front to rear vertical sectional view taken at the right-hand side of the machine in a plane substantially on the line 3--3 of Fig. 1.

Fig. 4 is a front to rear sectional view at the left-hand side of the machine taken in a plane substantially on the line 4-4 of Fig. 1 showing 3 details of the actuating mechanism for one of the ordinal columns of keys.

Fig. 5 is a front to rear sectional view taken at the left side of the machine in a plane substantially on the line 55 of Fig. 1.

.Fig. 5a is a fragmentary view similar to Fig. 5 but showing the toggle mechanism in locked condition.

Fig. 6 is a side view of the ordinal actuating mechanism as viewed from the left-hand side showing the mechanism set for an additive or positive operation.

Fig. '7 is a view similar to Fig. 6 but showing the actuating mechanism set for a subtractive or negative operation.

Fig. 8 is a fragmentary front to rear vertical sectional view of the machine taken in substantially the same plane as Fig. '7 with certain parts omitted to more clearly show the stop bar selecting means. 1

Fig. 9 is a transverse sectional view of the stop bar selecting mechanism taken me plane substantially on the line 9-9 of Fig. 8.

Fig. 10 is a'detail view of the manually operable means for setting the machine for additive or subtractive operations.

Fig. 11 is a fragmentary sectional view taken in a plane substantially on the line i l-H of Fig. 9.

Fig. 12 is a fragmentary sectional view taken iria plane substantially on the line lZ-l2 of Fig. 9. i

Fig. 13 is a detail view of the locking element for the stop bar selector guide lever.

Fig. 14 is a fragmentary transverse sectional view of the machine taken in a plane substan tially on the line l4l4 of Fig. 3.

Fig. 15 is a fragmentary sectional view of the "9" key control means'taken in a vertical plane substantially on the line I 5-15 of Fig. 1 showing the parts in their normal position when the machine is set for adding.

Figl 16 is a sectional view similar to Fig. 15 but showing the parts set for a subtractive operation. Fig. 17 is a sectional view similar to Fig. 16 showing the associated digital key depressed.

Fig. 18 is a fragmentary sectional view taken in a plane substantially on the line 13-48 of Fig. 14.

While the invention is susceptible of various modifications and alternative constructions, I have shown in the drawings and will herein describe in detail the preferred embodiment, but it is to be understood that I do'not thereby intend to limit the invention to the specific form disclosed, but intend to cover all modifications and alternative constructions falling within the spirit and scope of the invention as expressed in the appended claims.

General constructionhereinafter described in detail, such operation being efiected'through the medium of digital keys 24. One column of keys is provided for each. de-

nominational order of the accumulator mecha nism, there being nine of the keys 24 in each col-' the frame-24 to thedisengaged position in which the accumulator mechanism is cleared or zero-- ized in well known manner.

Inthe exemplary machine the keys 2% are mounted in a key frame 25 forming the top wall of a casing 2i within which the various mechanisms are supported by skeleton frame members or partition plates 23 (Figs. 3-5). Windows 29 (Fig. 1) in the top of the casing adjacent the front end thereof expose the number wheels to View. As'shown in Fig. 1 an additional window 28' is provided to the left of the window for the highest denominational numeral wheel to accommodate an overflow numeral wheel 22.

As herein shown, the key frame 26 is formed of generally rectangular plates 34, 32, and 3 3 (Figs. 3 and 14-17) suitably secured together and held in parallel spaced relation by'posts 35. Each of the keys 24 is provided with an elongated flat stem" 36 adapted to extend through alined slots in the frame plates for cooperation with the actuating mechanism 23. The keys are yieldably urged upwardly by individual springs 3i mounted on lugs 38 struck up from the plate 33 as shown in Figs. 1l-1'7. The free ends of the springs engage in notches formed in the edges of the stems 36 so as to lie crosswise of the slots in the frame plates 32 and 33 and thus serve additionally to define the upper and lower limit positions of the keys.

Each key 24 when depressed serves to impart a predetermined degree of digital actuation to the accumulator mechanism as indicated by appr0- priate rotation of the numeral wheel 22 of t e denominational order with which the depressed key is associated. Thus each row of keys is adapted to impart rotation to an accumulator actuating pinion ii (Fig. 4) journaled on a cross shaft 42 that extends across the machine and is supported by the frame members 28. Rotation of the pinion 4| in one direction is transmitted through an internal ratchet mechanism to a combined lantern wheel and accumulator gear 43 (Figs. 4 and 5) also journaled on the shaft 42. The lantern wheel gear is arranged to drive the associated numeral wheel 22 through the medium of a carryin gear (not shown) an intermediate gear 44 (Fig. 5) and a pinion 45 rigid with the numeral wheel, the gears being carried by the rock frame 24.

Carrying mechanism is provided in each denominational order of the accumulator'mechanism for imparting a digital unit of actuation thereto each time that a tens transfer is to take place from a lower to a higher denominational order of the accumulator. This mechanism is shown and described in my prior Patent No. 1,357,748 to which reference may be had for a complete description of the construction and mode of operation. Briefly, the carrying mechanism includes a carrying cam member 46 (Fig.

5) which is given a 180 rotation by a suitable carrying motor spring 41 associated with the carrying gear of the next lower denominational order for each tens transfer that is to be effected. The carrying cam member 46 acts upon a dolly roll 48 secured to a bell crank carrying-lever 49 to rock the latter in a clockwise direction as viewed in Fig. 5. Such rocking of the carrying lever 49 operates through a carrying pawl 59 pivotally mounted on the lever to throw the lantern wheel 43 a suificient distance to impart through the train of gears a digital unit of actuation to the numeral wheel 22.

Actuating mechanism In carrying out the invention, the actuatingmechanisms 23 by which the movements of the keys 24 are transmitted to the accumulator mechanisms are constructed and arranged so that the operation of each key may be registered either as a positive value for use in addition or multiplication or a negative value for use in subtraction or division. More specifically, the actuating mechanisms are so constructed and arranged that they may be selectively set to transmit to the associated numeral wheel of the accumulator mechanism upon depression of a key a degree of movement effective to register either the numerical value of the key or the complement of that value. Thus in each ordinal column of keys, except the first, the actuating mechanism may be set so that the depression of the 1 key will register either 1 or 8. The 2 key either 2 or 7, etc. In the first ordinal column of keys the selective setting of the actuating mechanism automatically conditions the 1 to register either 1 or 9. The 2 either 2 or 8, etc. Since negative values may be registered for subtraction or division by depressing the same keys used for registering positive values for addition, the keys may be designated by a single numeral. The uni-marked keyboard thus provided materially simplifies the performance of negative calculations such as subtraction or division and enables such calculations to be performed by the same simple touch system used for adding and multiplication.

As the actuating mechanisms 26 for the several denominational orders of the accumulator are alike, a description of one will suffice. Referring to Figs. 4, 6 and '7 of the drawings, the actuating mechanism provided for each denominational order comprises a prime actuator in the form of a gear sector 5| pivotally supported on a shaft 52 extending across the machine adjacent the front end thereof. The gear teeth of the sector mesh with the teeth of the actuating pinion M of the accumulator mechanism which, as explained heretofore, is coupled with the lantern Wheel 43 through the medium of a pawl and ratchet mechanism. A link 53 secured at one end to a depending arm 54 rigid with the sector 5| connects the sector with the depending arm 55 of a bell crank 56 pivotally supported by a rod 56' extending across the machine and supported in the frame plates 28. The other arm 5'! of the bell crank lever 55 projects forwardly below the key frame 26 to a point substantially in alinement with the 5 key of the ordinal column of keys with which it is associated.

Pivotally supported at 58 adjacent the forward end of the lever arm 51 is a balanced lever 58 extending longitudinally of the ordinal row of keys 24 and positioned for engagement by the lower ends of the key stems 36 .upon de ression of the keys. Rocking of the lever 59 relative to the arm 51 in a clockwise direction (as viewed in Fig. 4) is limited by a lug 69 projecting laterally from the upper edge of the arm to overlie the rear end of the lever. Provision is made for selectively limiting the relative rocking movement of the lever in the opposite direction, such means including a locking dog 6! pivotally mounted on the arm 5'! so that its notched upper end 62 may be swung under a pin 63 projecting laterally from the lever adjacent its rear end. With the dog thus set for engagement with the pin 63 the lever 59 constitutes in effect an extension of the arm 51 so that the keys 1 and 9 when depressed impart a progressively increasing degree of movement to the bell crank lever 56. As shown in Fig. 4 the upper end of the notched dog 6| is spaced from the pin 63 so as to permit a small downward movement of the rear end of the lever 59, thus slightly increasing the range of movement of the keys 6 to 9 as compared with the movements of the lower numbered keys which engage the lever 59 forwardly of its pivotal point 59. This small variation in the degree of key movement has been found advantageous in practice.

The motion thus imparted to the bell crank 56 is transmitted through the link 53 to the sector 5| rocking the latmr downwardly or in a clockwise direction as viewed in Fig. 4. The pinion 4| with which the sector gear meshes is correspondingly rotated but no rotation is imparted to the lantern wheel 23 because of the ratchet connection provided between the pinion and the wheel. Upon return movement of the sector the pinion and lantern wheel are rotated an amount determined by the displacement of the sector, thus registering on the numeral wheel 22 the value of the key depressed. Return of the sector is effected by a spring 64 anchored at one end to a stationary part of the machine and at the other end to a stud 65 rigid with the sector. Thus actual operation of the accumulator mechanism is effected uniformly irrespective of the manner in which the keys are manipulated, since the operation is effected through the medium of the power stored up in the spring 64 incident to the depression of the keys and takes place upon the release of the keys.

To permit registration of complemental values for negative calculations such as subtraction and division provision is made for changing the leverage ratio of the lever system through which the movements of the keys are transmitted to the accumulator mechanism. More specifically, provision is made for shifting the fulcrum of the lever 59 so as to substantially reverse the extent of movement imparted to the lever system and sector 5| by the respective keys. For this purpose the lever is provided at its forward end with a fulcrum stud 55, and a latch link 51 is pivotally supported on the sector 5! so that it may be hooked over the stud or disengaged therefrom as required. A link 63 connects the latch link 61 with the locking dog 5! so that when one of these fulcrum elements is shifted to its active position the other is simultaneously shifted to its inactive position.

With the latch link 6! hooked over the stud 66 the locking dog 6! is consequently rocked forwardly out of the path of the pin 63 at the opposite end of the lever 59. Depression of a key 24 accordingly rocks the lever about the axis of the stud 55 and the lever, through its pivotal connection 58 with the bell crank 55, rocks the latter about its pivot as shown in Fig. '7. The action in this instance is substantially the reverse of that obtained when the locking dog 6| is engaged since the "1 key impart maximum displacement to the linkage while the 9 imparts minimum displacement thereto. As indicated above, the leverage ratios are such that the complemental values'of the keys are registered on the number wheels 22.

Digital control To insure accurate registration of the numerical values represented by the several keys 24 of each ordinal column, means is provided for positively controlling the degree of actuation of the sector gear upon depression of any key. This means as herein shown is generally similar to that utilized heretofore in power driven calculating machines as disclosed in my copending application Serial No. 494,907, filed July 16, 1943, and comprises a pair of stop bars H and 12 (Figs. 6-9, 14 and 18) adapted to be coupled selectively with the gear sector 5! for positive andnegative calculations respectively.

As shown in Figs. 8 and 18 the stop bars 'H and 72 comprise elongated sheet metal strips of angular cross section supported below and at one side of the column of keys with one flange disposed substantially parallel to the key frame 26 and the other flange disposed in a vertical plane. In the exemplary embodiment the bar I2 is located below and within the angle formed by the bar H and both are supported for endwise sliding movement by lugs 53 struck out from the frame members 28 (Figs. 8 and 14).

Formed'on the upper flange of each of the stop bars ii and i2 are a series of lugs i i and projecting'laterally forengagement with the stems of the key 24 when the latter are depressed so as to limit the forward movementof the bars. The lugs M of the stop bar ii are spaced apart as shown in Fig. 18 so that the movement of the bar'increases progressively for the keys 1-9, the degree of. movement in each instance being such that the numerical value of each key is registered accurately on the associated numeral wheel 22. The lugs '55 of the stop bar i2 are correspondingly spaced apart, but the relative location of the lugs is such that the complements of the numerical values of the keys are registered on the associated numeral wheels 22. Thus the lugs F5 are so positioned in all orders except the units order to permit key movement to add 8 on the depression of a 1 key, '7 on depression of a "2 key, etc. In the units order, the lugs are so positioned as to permit key movement to add 1 on depression of the 9 key, 2.0n depression of an 8 key, etc.

To enable the stop bars to perform their control functions, provision is made for coupling the bars selectively with the gear sector 5! for movement therewith. Such selective coupling is effected through the medium of a link 16 (Figs. 8 and 9) pivotally connected at one end to an arm ll rigid with the sector 5! and having at its other end a laterally projecting stud 58' carrying a generally rectangular collar '59 (Figs. 9 and 11) The collar is is adapted to fit snugly between a pair of spaced fingers 5! (Fig. 11) rigid with the stop bar H or, alternatively between a pair of spaced fingers 82 rigid with the stop bar '52. The latter fingers are formed on and project downwardly from the vertical flange of the stop bar 12 in laterally ofiset relation as shown in Fig. 9 while the fingers t! are bent up from the lower edge of atab 63 integral with and depending from'the vertical flange of the stop bar I l. Thus the fingers 8| and 82 aredisposed in a common plane and, as theyare located so as to be in alinement when the stop bars are. in their normal positions, the collar H may be shifted vertically into engagement with either set of fingers to effectually couple the associated stop bar to the gear sector 5! to place the sector under control of the selected bar.

Setting mechanism Means is provided for effecting a simultaneous selective setting of the lever system and the selective coupling of the stop bars with the gear sector 5| to condition the machine for either positive or negative operation as required. Such means as herein shown comprises a manuallyoperable rock shaft 85 (Figs. 6 and '7) extending transversely across the machine and suitably journaled in the frame plates 28. For adjusting the leverage mechanism or in other words shifting the fulcrum of the lever 59 from the positive or adding position as shown in Fig. 4 to the negative or subtracting position shown in Fig. 7, the shaft 85 is provided with a radially projecting arm 86 connected by a link 8'! with a downwardly projecting arm 88 fast on a second transverse shaft 89. The latter shaft extends entirely across the machine below the locking dogs 6! and is provided with a series of upwardly projecting arms 90, one for each ordinal column of keys, and each adapted to engage a pin 9i on an extension 92 of the lower end of the locking dog 6! of the associated column.

Springs as connected between the lever arms 51 and the locking dog it yieldably hold the dogs in their positive or adding position with their ends 52 in blocking relation to the pins 63 of the balanced levers 59. When the shaft 85 is rocked clockwise from the position shown in Figs. 4 and 6 the arms 91! are rocked in the opposite direction and act through'the pins 9| to shift the locking dogs 6! and the latch links til coupled therewith to the negative or subtracting position shown in Fig. 7. The lever system is thus conditioned for transmitting the complemental values of the keys to the accumulator mechanism.

Simultaneously with the adjustment of the leverage system, the connecting link 16 is shifted from engagement with the positive stop bar H into engagement with the negative stop bar 12 to. operatively couple the latter with the gear sector 5!. The shifting of the connecting link is effected in each ordinal column through the medium of a rigid link 94 (Fig. 8) connected at one end to an arm 95 rigid with the shaft 85 and at the other end to a switch guide lever 96 pivoted at its front end on a stud 9'5 fixed in the machine frame. The guide lever extends alongside the link It andis formed at its free end with a slot 98 (Fig. 12) adapted to receive a grooved roller 99 mounted on the outer end of the stud 18 carrying the collar 79. As the guide lever 96 is rocked upwardly in response to the rocking of the shaft (35 the collar is thus shifted from engagement with the fingers 81' into engagement with the fingers 82 of the negative stop bar [2.

Provision is made for locking the stop bars H and 12 against accidental movement when either is disengaged from the gear sector 5i. For this purpose an elongated locking lever it! (Fig. 8) is pivotally supported intermediate its ends on the adjacent frame member 28. The locking lever is formed at opposite ends with outwardly bent lugs use and H33 engageable respectively in notches I04 and 15 formed in the vertical flanges of the stop bars 'II and 12. Thus when the machine is set for positive operation the lug I02 is entered in the notch I34 to lock the negative stop bar I2 in inactive position. When the machine is set for negative operation the locking lever is rocked about its pivot to withdraw the lug I32 from the notch I94 thus freeing the negative stop bar and entering the lug I I33 in notch IE5 to lock the positive stop bar in inactive position. Positioning of the locking element is effected by a pin I36 projecting laterally from the guide lever 35 and engaging in a slotted jaw IIl'I formed in the end of the latch element below the lug I33.

Provision is also made for holding the operated latch links 61 in their operative positions incident to the rocking of the shaft 85 in the manner above described. This is effected by elongated latch elements H (Figs. 4, 6 and '7) each pivotally mounted intermediate its ends upon and adjacent to the forward end of the actuating lever 59 with whichthe latch link 67 is associated. Each latch element H0 is formed at its rear end with a laterally bent tailpiece HI projecting through a slot H2 in the associated lever 59 for engagement with a hook-shaped lug H3 formed on the guide lever 95. When the machine is set for positive operation the guide lever is in its lower position and the lug H3 acts to hold the latch H0 in a withdrawn position as shown in Fig. 4. As the guide lever is rocked upwardly to condition the machine for negative operation the lug H3 is withdrawn from engagement with the tailpiece III thus permitting the latch element to rock clockwise under the action of a spring H4 and thereby present its forward end in blocking relation to a latch lug H5 formed on and projecting laterally from the upper end of the latch lever 67 as shown in Fig. 7.

In order to prevent the guide lever 95 from being shifted between the positive and negative positions while an actuating movement is taking place in any denominational order, each lever is formed with a laterally projecting lug i I5 (Figs. 4, 7, 8 and 13) positioned for engagement by a latch element Ill. The latter element is pivotally supported at its lower end on a rod H8 extending transversely across the machine frame and is provided at its upper end with a forwardly projecting latch finger H3 adapted to be positioned in the path of the lug H6. A spring I21] yieldably urges the latch element against a pin I2I carried by the link I5 which, when the machine is idle, holds the finger II9 clear of the latch lug H6. During an actuating movement the sector 5| is rocked downwardly and the link I6 moves upwardly with it, thus permitting the latch finger to move under or over the lug H6, depending upon whether the guide lever is in its upper or its lower position. In either case the lever is prevented from moving to its alternate position until the actuating movement is completed and the sector and link It have returned to their normal rest positions.

Setting means Manually operable means is provided for rocking the shaft 85 to change the machine from positive to negative operation. In the exemplary machine, two separate finger keys are provided for this purpose-one key IZI (Figs. 1, 2, 5 and 5 and I38 of the links.

a til;

division and subtraction. Thus in divisionit is necessary to make a record of the number of times subtraction takes place as well as the remainder, whereas in subtraction only the remainder is of any importance. The mechanisms associated with the keys I2I and I22 condition the machine automatically for meeting those different requirements as will be described hereinafter.

Provision is made for automatically resetting the machine for positive operation after each subtraction'or each time the machine is cleared. In addition, a manually operable key I23 designated by a plus sign is provided for resetting from negative to positive operation to allow for correction of inadvertent or erroneous actuation of the division key.

The division key I2I and the addition key I23 are arranged together at the left side of the ma.- chine as shown in Fig. 1. The keys are provided with fiat stems I24 and I25 (Figs. 5 and 10) slidably supported in the key frame 26 and having their lower ends pivotally operative with opposite ends of a walking beam lever I26. The lever is supported intermediate its ends by a pivot shaft I27 carried in the machine frame so that depression of the division key I2I is effective to rock the lever counterclockwise while depression of the addition key I23 rocks the lever clockwise as viewed in the drawings. Move- -ments of the lever are transmitted to the shaft 85 through the medium of a link I28 pivotally connected at one end to the lever and having a lost motion connection at the other end with an arm I29 rigid with and projecting radially from the left end of the shaft. The lost motion connection is provided in this instance by a pin I30 (Fig. 10) carried by the arm I29 and engaging in a longitudinal slot I3I formed'in the link adjacent its lower end. A spring I32 connected between the arm I29 and the link I28 yieldably holds the pin in the upper end of the slot.

Means is provided for releasably locking the shaft 85 in the operated position to which it is rocked by the depression of the key I 2|. The locking means, as herein shown, comprises a toggle mechanism including a pair of links I33 and I34 pivotally connected together at their adjacent ends by a stud I35. The outer end of the link I33 is pivotally connected by a stud I36 to an extension I31 of the arm I29 while the corresponding end of the link I34 is pivotally secured to the machine frame by a short shaft A spring I39 connected between the machine frame and the pivot pin I36 serves to lock the toggle when the links I33 and I34 are extended as shown in'Fig. 5a, the center pivot I35 then being below a line through the pivots I36 The spring additionally serves to rock the shaft back to normal when the toggle lock is broken. To prevent movement of the links beyond the locked position, the pivot pin I36 is extended to serve as a stop for the link I34 which is formed with a gooseneck extension I 4i! adapted to engage the stud.

The shaft 85 may be returned to the positive or adding position from the negative position above described if set by the division key by depression of the positive key I23. Depression of this key rocks the lever I26 clockwise, 'lift ing the link I23 which, by reason of its pin and slot connection with the arm I29, is free to move while the shaft remains locked in operated position. The link I28 is formed with a laterally guides bent lug I46 whichprojects under the extended end portion IMl of the front end of the link I34 131$ shownin Fig. a and is adapted to engage and additional settingfunctions required only for the subtractive operation. 7 a

- As shown in Fig. 3 of the drawings, the key I2 2 is provided with a flat stem I4I slidably mountedin the key frame 26 and is yieldably ur ed to its upper or normal position by a spring I42 similar to the springs 31 heretoforedescribed.

At its lower end, .the key stem I4I engages an arcuatelaterally projecting lug I43 rigid with a lever arm I44 which forms apart of a multiarmedlever I45 supported on the machine frame by a pivot stud I46. The lever I45 is operatively connected with the setting shaft 85 by a link I41 pivotally secured at one end to a depending arm I48 of the lever by means of a stud I49 and having a pin and slot connection I50 with a radially projecting arm I5I faston the shaft 85. The arrangement is such that the depression of the key I22 is effective to rock the shaft 85 to operated position in which it is locked by the toggle mechanism previously described.

Means is provided for yieldably latching the lever I45 in either the normal or operated position. For this purpose the arm I46 is formed at its outer end with an enlarged head portion I52 (Fig. 3) having a pair of outwardly facing V- notches I53 and I54 spaced apart for cooperation alternately with a centering pin I55. The centering pin is carried atjone end of'a centering lever I56 pivoted on the machine frame and urged by aspring'l51 in a direction to hold the centering pin in one or the other of the notches.

Upon such conditioning, "subtraction is effected bymanipulation of ahand lever I58 (Figs. 1 and 2) as will appear presently.

To prevent actuation of the accumulator meehanismimmediately upon release of a depressed digital key, means is provided for latching the mechanism against operation until the subtraction lever I5Bis actuated. The latching means, as shown'in Fig. 5, comprises a'series of elongated hook-shaped latchfingers I6I, one for each denominational order. Each of the latch fingers is pivotally supported on the machine frame and is urged by a spring into locking engagement with the lantern wheel 43 of the order with which it is associated. The latch fingers I6I are normally held in disengaged position by radially projectinglugs I63 carried by a rock shaft I64 and engaging rearward extensions I65 of the respective fingers.

The shaft I64 extends transversely across the machine frame adjacent the front of the mai2 chine and is normally held in a latch disengaging position .by a locking dog I66 (Fig. 3) pivotally supported on the machine frame and coacting with a single toothed locking element I61 fast on the shaft. A link I68 connects the dog with an upwardly projecting arm I69 of the lever I45, and a spring I10 acting on thelink normally holds the dog in locking relation to the element I61.

Upon depression of the subtraction key I22 the lever I45 is rocked clockwise withdrawing the dog I56 from looking positionv and permitting the shaft I64 to turn under the force exerted by the spring biased latch elements IGI (Fig. 5) as the latter move into locking engagement with the lantern wheels 43. Accordingly, return movement of the operated sectors 5| is prevented, the sectors being held in their depressed positions as determined by the particular digital keys operated.

Provision is also made for latching the depressed digital keys in their depressed positions pending the completion of the subtractive operation. For this purpose the stop lugs 15 of the negative stop bars 12 are provided at their front edges with forwardly projecting lugs I1I (Figs. 7 and 18) adapted upon movement of the bars to operated position to engage in slots I12 (Fig. '1) in the key stems. As the stop bars are coupled directly to the gear sectors they are, of course, held in operated position while the lantern wheels are locked and the depressed keys are consequently prevented from rising prematurely by presence of the lug I1I in the slots I12 which prevent full return of such depressed keys.

In performing subtractive operations on keydriven calculating machines as heretofore constructed, it is necessary for the operator to ignore the numeral 9 when it occurs in the subtrahend in any order except the rightmost order to be operated, in which case it is diminished by one and registered as 8. The complication involved in distinguishing between the orders in whichthe 9's occur is obviated in the present calculating machine in which the 9s keys are operated just like any other key in entering a subtrahend. To provide for registration of the proper values under such conditions means is provided for'automatically locking the actuating mechanism against operation by the 9s keys of all orders above the unit order while permitting sufficient operative movements of the keys to satisfy the operator that action has taken place by the nine key being locked downwhen so depressed. This locking mechanism is conditioned for action by the depression of the subtraction key I22.

The 9s key locking mechanism as shown in Figs. 14-17 comprises a thrust lever I15 for each denominational order except the units order at the extreme right side of the keyboard. The levers are alike in construction, eachbeing formed at one end with laterally projecting lugs I16 adapted to engage in guide slots in the key frame plates 33 and 34. Forwardly of the lug 16iare opposed radial surfaces I11 adapted to engage the frame plates and provide a shifting pivot "for the lever. A torsion'spring I18 carried by a stud I19 located centrally of the surfaces I11 and having its ends engaged respectively under a stop lug 80 on the lever and in' a hole in the frame plate 34 urges the lever rearwardly in the guide slots and tends eto raise the rear end to the position shown in Fig. 15. V

Intermediate the ends of the lever' I15 "the upper edge portion is bent over to form a laterally projecting lip I8I normally positioned at the rear of the stem of the associated digital key and adapted to enter a notch I82 in the side edge of the key stem when the lever is shifted forwardly. The extreme end portion of the lever forming the lip is further bent to form a vertically disposed depending head I83 guided in a slot I84 in the frame plate 34. When the lever I is rocked to the operated position shown in Fig. 17 the head I83 is moved into blocking relation to a pair of laterally projecting lugs I85 and I86 formed respectively on the stop bars H and 12 and is thereby effective to lock the bars against forward movement.

Rocking of the lever 15 is effected by depression of the associated 9s key through the connection provided by the lip I8! engaging in the slot I82. It will be apparent that the lever is operative to limit the downward movement of the associated digital key as well as the forward movement of the stop bars 1! and 12 so that no actuating movement is imparted to the actuating mechanism and consequently no operation of the accumulator mechanism occurs upon depression of a 9's key in orders other than the units order. In subtraction, depression of a 9 key in the units order adds its complement l.

The lever I15 is normally held in an inactive position by the spring I19 which urges the lever rearwardly so that the lip MI is withdrawn from the notch I82 as shown in Fig. 15. The forward shifting of the lever to condition it for operation is effected as an incident to the rocking of the subtraction lever I45 by the subtraction key I22 (see Fig. 3). For this purpose the lever arm I48 is connected by a link I81 with an arm I88 fast on a rock shaft I89 extending transversely across the machine frame at the rear of the machine.

Referring to Figs. 15-18 of the drawings, the shaft I89 is provided with a series of radially projecting lugs I98, one for each denominational order except the first or units order. Each lug 1S operative when the shaft is rocked (counterclockwise as viewed in Figs. 15-17) to engage a.

pivoted lever I9I and swing its lower bent lip forwardly against the rear edge of the head I83 thereby shifting the lever I15 forwardly to the working position in which it is shown in Fig. 16.

A second series of lugs I92 projecting from the opposite side of the shaft I89 includes a lug for each denominational order except the first. Each lug I92 is arranged to coact with a depending finger I93 formed on a latch element I94 pivotally supported on the machine frame above the free end of the lever I15. When the machine is set for positive operation the shaft I89 is positioned so that the lug I92 acts to hold the latch element in disengaged position as disclosed in Fig. 15. When the shaft I89 is rocked to the negative calculating position, the latch element is rocked by a spring I94 into engagement with the forward edge of an upstanding lug I95 formed at the rear of the lever I15. Upon depression of the lever, the latch element swings over and in blocking relation to the top of the lug as shown in Fig. 17 and thus prevents return of the lever and key to their position when the digital key is released.

As stated heretofore, the actual subtracting operation is effected by manipulation of the subtraction lever 558 after the subtrahend has been fully set up on the keyboard. Referring to Fig. 3 of the drawings, the subtraction lever is keyed to a hub 2M rigid with an arm 202 loosely mounted on a rock shaft 203 journaled in the machine frame and extending transversely thereaoross. Another arm 204 fixed to the shaft and operating close in line with the arm 282 is connected therewith by a toggle lock formed by links 295 and 296 pivotally interconnected in the usual manner. When the toggle is locked as shown in Fig. 3, the subtraction lever is operatively connected with the shaft and effective to rock it in an anticlockwise direction when the lever is pulled forwardly by the operator, as shown in Fig. 3.

The shaft its is normally locked against opr eration by a locking dog 281 pivotally supported on the machine frame and urged by a spring 208 into blocking relation to a lug 209 rigid with and projecting from one end of the arm 204. The locking dog 291 is retracted to release the shaft 283 for operation incident to the depression of the subtraction key I22. Such retraction is effected by a link ZI! connected at one end to the dog and having at its other end a slot 2 I2 adapted to receive the projecting end of the stud I49 carried by the lever arm I48.

Auxiliary and universal power mechanism With the machine conditioned for subtraction as above described, and the subtrahend entered on the keyboard, the subtractive operation is carried out by pulling the hand lever I58 forwardly and thereby supplying auxiliary and universal power by rocking the shaft 283 in a counterclockwise direction as viewed in Fig. 3, or clockwise as viewed in Figs. 4 and 5. One result of the rocking of the shaft 253 is the application of power for the addition of 9s in all orders (10 in the units order) not preset or locked in the setting of the subtrahend to register the complete complement of the subtrahend and thus leave the correct remainder showing on the numeral wheels of the accumulator.

The mechanism for automatically supplying power for adding 9s in orders above the unit and 10 in the units order includes a series of levers 225 (Fig. l) each pivotally supported on the actuator lever supporting pivot Shaft 56' and having alaterally hent iug 216 at its free end overlying the upper edge of the associated actuator lever 55. Each lever 2 I5 is operatively connected by a coiled spring 2i1 with an arm 2I8 fast on the auxiliary power shaft 253. As herein shown, the spring 2I1 is anchored at its lower end to a link or ram 2 I9 pivotally secured to the arm 2I8 and projecting axially through the coiled spring. The other end of the spring is anchored to a stud 220 projecting laterally from the associated lever 2 I5.

The ram 2I9 is of a length such that its upper end normally engages the stud 229 and holds the lever 2I5 slightly elevated so that normally no pressure of the power unit is exerted on the actuating lever 55. When the auxiliary power shaft is rocked, the rams 249 are pulled down thus allowing the levers 2I5 to move under the influence of the actuating springs 2 I 1 and depress the actuating levers 56 sufficiently to add ten in the units order and nine in all other orders in which the actuating levers are not locked by the setting of the subtrahend. In the case of locked levers the actuating springs 2I1 yield without imparting movement thereto.

The movements of the depressed actuating levers 56 are transmitted to their gear sectors 5| 1 for operating the accumulator mechanisms in asrzoce is the manner heretofore described. Tomini'mize the force required for that-purpose and thus facilitate the setting of the gear sectors by the levers-2'l.5,* means is provided for temporarily relieving-the tension of the sector actuating springs 64. To this end leach spring 64 is coiled around :an' elongated link or ram 22! (Figs. 4 and 6) and the fixed end of the spring is secured thereto as bythreading overa-notched section 222 adjacent the outer end of the ram. The said outer end of the ram is secured by a lost motion connection to an arm 2|23fast ona'rock shaft 224 journaled in the machine frame, such connection being provided-by a stud 225 on the arm engaging in a slot 226 in the ram. The arrangement is such that when the shaft 22% is in its normal position as sh'oWnin-Fig. 4, the forward end of the ram just clears the stud 65 which anchors the actuat- I ring-,spring'to its sector I. As the shaft is rocked toward the operatedposition, the ram is permitted to move forwardly-against the stud and thusrelieve the tension of the spring. In the vca'se'of sectors that have been preset in the setting up of the subtrahend, this relief of tension has no effect as such sectors are locked in place as heretofore explained and the stud 225 merely moves along the slot 225. The other sectors may then .be rocked through the action of the 9s auxiliaryactuating mechanism Without requiring the application of anexcessive amount of power.

The rocking of the shaft 22 to its spring released position is effected as an incident to the actuation of theauxiliary power actuating lever .I58-and the shaft is automatically returned to normal rest position at a precisely timed point in the cycle of its operation to complete the auxiliary power operation. Such movements of the shaft 222 are controlled by a toggle mechanism including apair of links 229 and 230 joined by a center pivot stud 23I as shown in Fig. 5. The forward .end of the link 229 is pivotally connected to a crank arm 232 rigid with the shaft 22% while the corresponding end of the companion link 23!! 'is pivoted on a short shaft 233 carried in the machine'frame. The link 2% is formed with an upwardly projecting arm 234 connected by a link ing the shaft 22 back .to normal position and restoring the full tension of the springs 6 during'the lastl/ of an inch of motion of the studs 225 as the toggle is exerting its greatest power action.

In the forward movement of the auxiliary power actuating lever I58,Ithe multi-armed lever I45 which was operated by depression of the subtraction key I22 is restored to the. normal position occupied when the machine is set for positive operation. Such return is effected by an offset arm 24! (Fig. 3).rigid with and projecting downwardly from .the'arm 26L The. arm 2 3! carries a stud 242 operating in and. adaptedto engage the lower end of a slot 243 in the-lower end of a link 2 55 which is pivotally connected at its upper end to a depending arm 2&5 of the lever I45. Return of the lever M5 to normal position restores the locking dog I56 to operative position and resets the latch 28'! for operation.

The return of the lever I45 also results in the retraction of the link It!v by which the shaft I was initially operated to condition the No.9 key when set toprevent actionin that order. To hold 'all set No. 9'keys inaction untilreturn of the into latching engagement with a toothed latch element 2&8 fast on the shaft E89. A link 249 having a lost motion connection at one end with the latch dog and pivotally connected at the otherend to an arm 250 rigid with the shaft 293 normally holds the latch element in a disengaging position. As the auxiliary power leveris pulled forwardly the link2l9 is raised, thus allowing the dog 246 to engage the latch element248 and lock the shaft I89 in an operated position. The return of the shaft I89 to normal position is effected through the action of the link 249 to retract the dog 24% as it returns to normal. and

thus release the shaft I89 for return movement.

Near the end of the action of the auxiliary power lever I58 the accumulator latch mechanism is released so that registration may take place upon restoration of the tension of the sector actuator springs M. The release of the accumulator latch mechanism is effected by the auxiliary power shaft 263 through the mediumof the arm 236 which is connected by a link 2.56 (Fig. 5) with an arm 25? fast on the latch control shaft E54. The connection with the arm..25I is providedby a stud 258 engaging in a slot 259 in the link so as to permit the control shaft to'b'e rocked to operated position by the subtraction key prior to the operation of the auxiliary .power lever. As the link 25% is drawn rearwardlydur- .ing the operationof the auxiliary power-lever,

the end of the slot engages the stud 258 and rocks the shaft I84 clockwise thereby causing the lugs nects the auxiliary power lever with its shaft '293 just at the instant the said lever reaches its full forward throw. Thus the shaft is released from the lever and control of the further action of it until the machine is again set for subtraction and .is so rendered independent of any further manipulative actions taken by the operator. The shaft 2fi3'when thus released is returned to normal rest position by a spring 2% anchored at one end to a stud 264.fixed on the machine frame and at the other end to a downward extension 255 of the, arm 204. In its'return movement the shaft 203 acts through the toggle links 229 and 23s to rock the shaft 224 counterclockwise, as viewed in Fig.

5, whereby the sector actuating springs 64 are retensioned. It may be noted-that in retensioning the springs it is only necessary to stretch them sufficiently to disengage their rams of an inch from the studs 55. This action is timed to occur just as the toggle links 22s and 236 are passing over their locking center at which point the forcemultiplying action of the toggle is at its maximum. The power for this operation is supplied, of course, "by the. spring "253 assisted by the tension of the springs 2 I Tin the denominaw 'theirset positions back to their normal rest .-.tions. In this return movement, the accumulator 17 tional orders in which the actuating mechanism has been preset or locked against operation.

The restoration of the tension of the springs 64 immediately serves to rock the sectors from posinumber wheels 22 are operated in the usual way to register the values represented by the setting of the sectors. In the case of sectors set for the registration of the subtrahend, the amounts transferred to the number wheels are the complements of the values represented by the digital keys actuated to set the sectors. In all other orders, except the first, 9 is registered in the accumulator mechanism, "10 being registered in the first order when required.

In order to prevent false operation of the overflow numeral wheel 22 where there is no actuating mechanism to clear away the carry of the tens which occurs under such a method of subtraction means is provided for preventing tens carrying-operation from the highest actuated denominational order. of the machine to such wheels. For this purpose the link 25% by which the accumulator latching elements are released,

Subtraction safety devices It is obvious that if, during subtraction, it were possible to operate the clearing or cancelling mechanism or to operate the addition setting key that mechanism would be displaced which would make subtraction impossible. Therefore, as a means of safety againstsuch an error, the clear ing or cancelling mechanism is locked as the subtraction key I22 is depressed. Likewise, through the same medium, the addition setting key 125 is looked as the subtraction setting key is depressed.

The means generally is not new in this invention as practically the same means is employed in my pending application Serial No. 494,907, herein previously referred to, and in the present case consists of the lock lever S pivoted at its lower end on a stud 3!! (see Fig. 3) fixed in the framework and connected near its upper end by a short link (not shown) to the arm 2'55. The arm 215 is fast on a short cross shaft 2%, with the result that when the cancellin lever M: S pulled forward the upper end of the lever Sit al o swung forward. It will be noted that the -ie other. Therefore, when the subtraction key l 22 is depressed or set, the lateral portion Bid of the arm of the multi-armed lexr 265 makes movement of cancellin lever 2a impossible. Or t e cancelling lever should be left partly operated, the subtraction key 522 cannot be do pressed, as the lateral extension 312 would block the upward swing of the arm 313 of the lever [$5,

thereby preventing the downward movement of Til tents ifii andrelatching of the lateral mg M3 by the shank MI of the subtraction key.

The locking of the addition setting key during subtraction is accomplished also by depression or" the subtraction key i 22. Ithas "been disclosed how the rock shaft I54 (see Fig.'"' 5) is rocked clockwise (as viewed in Fig. 3) when released by its detaining dog 66 (Fig. 3). t the left end of the said shaft the arm 25! keyed to said shaft through i s stud 258 operates a link 3253 by means of slot the sin to pull thesaid link forward. The rear end of said link is pivotally connected to the upper left end 32! of a lock lever having two upstanding arms, one to which the link is connected, as stated, and another, 222, to the ri t thereof which, when the shank I25 of the addition setting key is raised by the setting of the subtraction key, underlies the lower end of said so that a spring 323 operating about the pivot 324 swings the raid arm under the key shank, looking it against depression until it' is again wi hdrawn from its locking position by the action of the link 255 in clearing the locking deshaft I64 by the lock,-

ing dog ifi S (Fig. 3). V

Resetting} for positive operation As positive forms of calculation such as addi} tion and multiplication ordinarily comprise about of the work in accounting, it has been found advantageous to provide for automatically-resetting the machine for positive operation after a negative operation. As described heretofore, such resetting is effected after a subtraction by restoration of the multi-armed lever M5 to its normal rest position and the release of various latches as an incident to the operation of the auxiliary power lever I58. The means by which the actuation toggle lock is broken and the actuation control shaft is re set for addition will now be explained. When the arm 233 on the power lever shaft 293 breaks the actuation'spring tension, the arm 232 on the shaft 225 by means of the pin 232 contacts the arm-13 of the toggle link breaking the toggle; above center, where it is caught ,dur ing this phase of the operation by a shouldered latch member 269 (Figs. 5, 5a and 10) which is allowed to move over a latching lug 27!? formed on the toggle link I34. The latch member normally held in a retracted position against spring tension by the pin 27! carried by the link 2555 and engaging a detent 212 rigid with the latch member. As the link is drawn rearwardly the detent and latch element follow under the influence of a spring 273. When the pin 27! returns with the link 256 the latch is removed, allowing the toggle to double up and rock the actuating control shaft 85 into an adding position. Resetting through the medium of the adding key I 2-3 has" also been described.

In addition to the foregoing, means is provided for resetting for positive operation in response to the clearing of -zeroizing oi the register. As explained heretofore, clearing of the register is effected by rocking the frame 24' away from the normal position shown in Fig. 5 to detrain the driving gears for the accumulator mechanism. Rocking of the frame 24 is eifected by the zeroizing lever 25- (Figs. 1 and 2) which is located at the right side of the machine and keyed to the projecting end of a short cross shaft 2Y4 (Fig. 3) journaled on the machine frame.

An arm 21% fast on the shaft is connected by a, li'nk'2l6 with an intermediate point on a lever 211 which is pivoted at one end on the machine frame and connected at the other end by a link 213 with an armfll) loosely mounted on a sha t 280 hereinafter called the zeroizing shaft. A lug projecting laterally from the arm 219. for engagement with a similar arm 219 fast on the shaft 286 provides a one-way connection whereby the shaft may be rocked to operated position as the zeroizing lever 25 is pulled forwardly and is permitted to remain in such position while the lever returns to normal rest position.

When rocked to operated position the shaft 2% swings the rock frame 24% to a zeroizing position through the medium of a series of links 281 (Fig. connected between. the frame. and arms 282 rigid with the shaft. A notched segmental extension 283 (Fig. 3) at the free end of the arm 215 cooperates with a double acting spring actuatedlocking pawl 2.84 in well known manner to compel operation of the zeroizing lever through a full stroke in each direction on each actuation. Means is provided for locking the Zeroizing shaft 230 in operated position pending the depression of a digit key to begin the next calculation. The locking means as shown in Fig. 5 of the drawings comprises a toggle lock mechanism including a pair of links 2&5 and 236 pivotally interconnected by a pivot stud 281. The link 285 is pivotally connected at its outer end to an arm 288 rigid with the shaft 28% while the link 286 is pivoted on a short shaft 2&9 mounted in the machine frame. The arrangement is such that the toggle links when str ightened out in a clearing action of the shaft 258. as described, move over a center position and look as the shaft approaches operated position, and the locked toggle accordingly acts to hold the shaft in such position.

When the togglelock is broken, the shaft 288 is returned to normal position by a spring 295 connecting between a stud in the arm 288 and the machine frame. For breaking the toggle lock there is provided a trip shaft 29! (Figs. 47) journal-ed in and extending transversely across the machine frame adjacent the rear end of the machine. A series of cam arms 292 fast on the shaft, one for each column of keys, are positioned for engagement by cam rolls 293 carried at the lower ends of the arms 55 of the bell crank actuating levers 56. As an incident to such rocking action the shaft 29! is rocked in a clockwise direction as viewed in Fig. 5.

The rocking movement of the trip shaft acts to break the toggle lock for the shaft 283 through the medium of an arm see (Fig. 5) fast on the trip haft and connected by the link 295 with an arm 2% pivotaily supported by the shaft 289 which supports the toggle link 236 and to which it is made fast. The connection between the link 295 and the arm 296 is provided by a stud 291 which is extended so the head may engage all upwardly projecting arm 298 formed on the toggle link. A spring 299 connected between the machine frame and an arm 30E rigid with the arm 296 urges the latter forwar .ly and serves to maintain the trip shaft and associated elements in an inactive position. As-the link 235 is drawn rearwardly by the trip shaft, the stud is operative to rock the toggle link 2533 over its locking center and thus break the toggle lock for the shaft 255. The latter, of course, is restored to normal position by the spring 2%, as heretofore explained. a

. For resetting the machine for positive opera- 20 tion, the toggle link is formed witha depend ing arm 5594 (Fig. 5) operative the movement of the toggle link to locking position to enga e a pin 3E2 (Figs. 5. and ill) projecting from the division key link i255 providing that the link is in its. lower or negative set position. Upon such engagement, the link 523 is shifted upwardly to break'the toggle lock for the subtraction shaft 35 as heretofore explained, which is immediately returned to the positive set position by the spring 13$. The machine is thus automatically conditioned for positive operation.

Operation Positive forms. of calculation such as addition and multiplication are in the same manner as with prior calculating machines. When the machine is set for positive calculation, the dog 6! and the lug lit, in effect, latch the rear end of the, balanced lever 59 to the bell crank lever 58 so that both levers rock as a unit about the fulcrum oft-he bell crank. The keys of orderv accordingly act through the lever s to rock. the lever 55 and thereby displace the sector gear 5i gradually increasing amounts in the order of progression of the key numbers so as to register in the accumulator mechanism the numerical values of depressed keys.

' The extent of displacement of th 5 l is controlled by the positive top.

sector gear er ii in the usual way and actuation of the accumulator of the Zeroizing lever to unless it is desired to add other totals to that accumulated.

The improved and simplified techniques by which negative calculations may be carried out with the improved calculating machine will be readily apparent from a consideration. of the op. erations involved in the solution of a few problems of the type commonly met with in ac counting practice. .As an example, assume that the operator ha accumulated the sum of 63,- 785154 on the register either by depression of the corresponding keys or by the addition of a plurality of smaller amounts and is required to subtract therefrom the amount 648375. Before entering the subtrahend, the subtraction key it is depressed to condition the machine for subtractive negative operation. Depression of the subtraction key I22 conditions the actuating mechanism 23 for regist ring values by setting the leverage system so as to substantially reverse the progression of the displacements imparted tothe sector gear by the keys 1-9 of the order. More particularly, the depression of the subtraction key withdraws the dog ti to release the rear end of the balanced lever ts from the bell crank lever 58 and establishes a fulcrum for the forward end of the lever by engaging the hooked end of. the latch element 51 over the stud 66 carried by the lever.

In addition to conditioning the actuating mechanism for negative operation, depression of the subtraction key switches the connection of the gear sector H from the positive stop bar H to the negative stop bar 12; releases the latch detents I51 for latching the sectors in key set positions; shifts the 9s key locking levers 15 to active position; and withdraws the latch element 2t? to free the auxiliary power lever H38 for manipulation. These conditioning actions are effected through the medium of the multiarmed 'compleinental' lever I45 and the associated control instrumengtalities associated with it.

*3. Havingset the machine for subtraction, the subtrahend is now entered on the keyboard, that Lis, keys 648.75 in the proper ordinal columns are depressed either successively or simultaneously as is most convenient. By reason of the negative setting of the actuating mechanism, the depression of the above keys displaces their sectors for th'e'addition of the complemental values, n'amely, 351.25 to the accumulator.

The adding of the ccmplemental values of the digitalkeys to register the subtrahend does not take place immediately upon the release of the keys as the actuating mechanisms associated therewith are locked in set positions by the accumulator latches I6 I. The keys themselves are latched in depressed positions by the latch lugs ill of the negative stop bars 12 so that the operator may readily check the accuracy of the figures set'for' registration.

Following the setting up of the subtrahend on the keyboard, the" auxiliary power lever i58 is pulled forward to furnish power for all orders and release the accumulator mechanism latches lfilso' that the subtrahend values may be transferred to the numeral Wheels 22 as the actuating mechanism sector gears 51 return to normal position under the spring actuation set up by the auxiliary power shaft movement. The forward movement of the auxiliary power lever also relieves the tension of all the sector gear actuating springs 64 and reconditions them again to register all orders of adding mechanisms for operation by depressing the bell crank levers 56 and displacing their associated sector gears 51 sufiiciently to add 9 in each previously unset order except the units order where'10 will be added if not preset. when the-auxiliary power lever :58 reaches its "forward limit position, the toggle lock with the subtraction shaft 203 is broken thus freeing the shaft for returnmovement independently of the lever under the influence of the spring 263. In the return of the auxiliary power shaft, the tension of the sector actuating springs is restored and the sectors are accordingly returned to normal position thereby transferring there set values to the numeral wheels. The levers 2L5 of the auxi iary power mechanism are released prior to the retensioning of the springs 54 so that all sectors are restored to normal at the same time.

In the specific problem set out above the values transferred to the numeral wheels are as follows:'

Register total or minuend H 63,785.64

subtrahend complement s. 351.25

Automatic 9s adding mechanism 99,000.00

Remainder shown on register 63,136.89

Assume by way of illustration that the amount to be subtracted from the above minuend is $43.00 instead or" 648.75 as in the previous problem. In that case the subtrahend complement is 351.00 and the operation includes the automatic addition of 10 in the units order as shown below:

Register total or minuend 63,785.64

setting up the minuend or for adding.

It will be observed that the operations above illustrated do not require the operator to remember any complemental key markings or to employ the dual touch system. The 'su'otrahends are set up by the same touch system used for Thus the operators work is greatly simplified, the likelihood of errors occurring is reduced and the speed with which negative calculations may be made is materially increased.

Y "A'further advantage is derived from the arfrom the 9 mentally and depress the eight key of the appropriate order. The mental calculations required to set up such subtrahend correctly are entirely eliminated by the improved machine since the operator is required to actuate a key for each 9 appearing but false registration thereof is automatically prevented by the key locking mechanisms. It will, be evident that the speed of operation is materially increased and the mental strain on the operator is substantially reduced.

While the foregoing explanations may leave the impression that the subtractive operation is a relatively slow one, it is actually much quicker than the method heretofore in use in which the rules had to be varied under differentconditions. Thus the operating method made possible by the improved calculating machine eliminates the necessity of selecting the proper carry cutout lever, the mental gymnastics of deciding when to register and when to ignore 9s in the subtrahend and the learning of a dual touch system as required for complementally or dual marked keyboards.

All such complications are eliminated leaving only the depression of keys having only one marked value and the simple operation of the subtraction key and the auxiliary power lever.

Division, which is simply a multiple subtractive operation, is carried out in the same manner as formerly which with the advantages inherent in the uni-marked keyboard greatly simplifies such calculation. All numerals appearing in the divisor are registered on the keyboard including the zeros for which the 9s keys are used. These keys are appropriately marked for the purpose by the small 0 located at the left of the 9. As the operation of the division key [2! conditions the actuating mechanism 23 forregistering complemental values and connects up the negative stop bar H without releasing the accumulator latches I61, the remainders appearon the numeral wheels immediately upon release of the depressed keys. Carrying of tens takes place as for adding and provides a visual indication of the result in the usual way.

It will be apparent from the foregoing that the invention provides a key-driven calculating machine of novel and advantageous construction. Through the provision of the novel means for selectively controlling the degree or actuation of the accumulator mechanism by the digital keys, the machine may be conditioned for either positive or negative operations by the use of a single touch system. In other Words, by conditioning the machine for the particular type of operation required, the use of dual marked keys and 

